GRUB_CMDLINE_LINUX_DEFAULT keeps boot parameters from installer

[Francois Lafont]

Hi,

I use ubuntu-20.04.3-live-server-amd64.iso from https://releases.ubuntu.com/20.04/ (sha256sum=8e3086f3cea0fb3fefb29937ab5ed9d19e767079633960ccb50e76153effc98) to make an automatic install of Ubuntu 20.04. Here is my user-data file:

```yaml
#cloud-config
autoinstall:
  version: 1
  locale: en_US.UTF-8
  keyboard:
    layout: fr
    variant: ""
  apt:
    preserve_sources_list: false
    primary:
      - arches: [amd64]
        uri: "http://archive.ubuntu.com/ubuntu"
    disable_suites: [backports]
    # Unfortunately, disable_components option is too recent to be supported
    # on Ubuntu 20.04.
    #
    # See: https://github.com/canonical/curtin/commit/02037187c142b41f9e993eefde615794827fd271
    #
    disable_components: [multiverse]
    geoip: false
  update: no # better to update during postinstall stage.
  packages: []
  network:
    network:
      version: 2
      ethernets:
        nics:
          match:
            name: 'ens*'
          dhcp4: true
  storage:
    swap:
      size: 0 # No swap, will created (or not) by cloud-init.
    config:
      - id: disk-root
        type: disk
        ptable: gpt
        path: /dev/sda
        wipe: superblock
        preserve: false
        grub_device: true
        name: disk-root
      - id: part-grub
        type: partition
        number: 1
        device: disk-root
        size: 1MB
        wipe: superblock
        preserve: false
        flag: bios_grub
        name: part-grub
      - id: part-root
        type: partition
        number: 2
        device: disk-root
        size: -1 # The remaining space.
        wipe: superblock
        preserve: false
        name: part-root
      - id: fs-root
        type: format
        fstype: ext4
        preserve: false
        extra_options: ["-E", "lazy_itable_init=0"]
        volume: part-root
        label: fs-root
      - id: mount-root
        type: mount
        spec: "LABEL=fs-root"
        path: /
        device: fs-root
        options: "noatime,errors=remount-ro"
    # Without this setting, the default value is true according to my research
    # and the option GRUB_CMDLINE_LINUX_DEFAULT in the config file /etc/default/grub
    # is set to the same boot options as the installer, ie something like
    # "autoinstall ds=nocloud-net;seedfrom=http://..." in my case.
    #grub:
    # replace_linux_default: false
  ssh:
    install-server: yes
  identity:
    username: ubuntu
    password: $6$b3fc746099763fbf$ooDi.9kU5tJbcHQCX.d2xuxWumgWzPZb9y7WMMmP6bLPPl3mosDlRXs5zpNtACCCx4gfoSzHL.eEACeS7U/M31
    hostname: template-ubuntu-20-04-all-in-one
  user-data:
    timezone: "Europe/Paris"
    hostname: template-ubuntu-20-04-all-in-one
```

After the installation, the machine has this line in the file /etc/default/grub:

```
GRUB_CMDLINE_LINUX_DEFAULT="autoinstall ds=nocloud-net;seedfrom=http://192.168.221.149:8449/"
```

This is exactly the boot parameters I use during the installation (via packer). To avoid this and keep the default value of GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub (ie ="quiet splash"), I have to uncomment these lines in my user-data:

```
    grub:
      replace_linux_default: false
```

In this case, I have `GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"` after the installation, the default value, and the expected value to me.

Is it normal?
Regards.

[Michael Hudson-Doyle (mwhudson)]

Curtin copies kernel command line arguments after --- to the installed system. So if you put the "autoinstall ds=nocloud-net;seedfrom=http://192.168.221.149:8449/" content before the --- then it should not be configured for the installed system. What is the complete command line you are passing to packer?

[Michael Hudson-Doyle (mwhudson)]

Oh looking at the source a bit, I think maybe the entire command line gets copied over if there is no --- present. So maybe just add " ---" to the end of the command line you are using?